Innovative exploration of phantom limb pain treatment based on extended reality technology

Table 2 Summary of key studies with extended reality in phantom limb pain

Ref.	Type of study design	VR/AR/MR	Intervention	Treatment duration	No. of sessions	Pain assessment	Pretreatment	Post-treatment	Treatment efficiency
Ortiz-Catalan et al[20], 2016 (n = 14)	Single-group clinical trial	AR/VR	Machine learning-based myoelectric control of virtual limb in AR/VR environments, including gaming tasks (e.g., racing car, target matching)	2 hours/session	12	NRS, PRI	NRS: 5.2 ± 1.6, PRI: 19.2 ± 10.5	NRS: 3.5 ± 2.1, PRI: 9.6 ± 8.1	50% of patients reduced medication intake; 71% reported ≥ 50% pain reduction at 6 months follow-up
Osumi et al[17], 2017 (n = 8)	Clinical trial	VR	VR system using head-mounted display to show mirror-reversed computer graphic image of intact arm, simulating phantom limb movement	10 minutes (single session)	1	NRS, SF-MPQ	NRS: 5.2 ± 2.4, SF-MPQ: 8.3 ± 7.6	NRS: 3.0 ± 2.1, SF-MPQ: 2.5 ± 3.2	39.1% reduction in NRS; 61.5% reduction in SF-MPQ
Lendaro et al[19], 2017 (n = 1)	Case study	VR	Phantom motor execution with myoelectric pattern recognition and virtual reality for lower-limb amputee	Approximately 2 hours/session	23	NRS, PRI	NRS: 4, PRI: 32	NRS: 2, PRI: 10	50% reduction in NRS; 68% reduction in PRI
Perry et al[22], 2018 (n = 8)	Clinical trial	VR	Virtual integration environment using electromyography to control virtual avatar limb movements	30 minutes/session	Average 18	VAS, SF-MPQ	VAS: Curve in figure, SF-MPQ: Curve in figure	VAS: Curve in figure, SF-MPQ: A curve in figure	88% of participants reported pain reduction; 29% sustained relief at 6 months
Rothgangel et al[23], 2018 (n = 75)	Single-blind RCT	AR	Group A: MT (4 weeks) + AR (6 weeks); group B: MT (4 weeks) + self-delivered MT (6 weeks); group C: Sensomotor exercises of intact limb (10 weeks)	10 weeks (4 weeks initial + 6 weeks follow-up)	10 individual sessions (first 4 weeks)	NRS	NRS: Mean 5.7	Group A: 4.6 (10 weeks), 4.1 (6 months); group B: 3.6 (10 weeks), 2.7 (6 months); group C: 4.1 (10 weeks), 4.5 (6 months)	No significant between-group differences in NRS; 3 patients in group B showed complete recovery of PLP at 6 months
Rutledge et al[18], 2019 (n = 14)	Feasibility study	VR	VR MT with bicycle pedaler and motion sensor to synchronize real/virtual limb motion	Single session (feasibility testing)	1	Phantom Limb Pain Questionnaire	57.1% (8/14) participants reported PLP; 93% (13/14) reported one or more unpleasant phantom sensations	28.6% (4/14) continued to report PLP symptoms and 28.6% (4/14) reported phantom sensations	Participants rated the treatment highly (75%) on the dimensions of helpfulness, immersion, realism, and satisfaction
Kulkarni et al[24], 2020 (n = 9)	Pilot study	VR	Immersive VR with virtual limb visualization and interactive tasks	55 minutes/session/months	3 sessions (3 month)	NRS	NRS: Mean 6.11	Mean NRS: 3.56	Reduction in NRS with no significant difference
Thøgersen et al[21], 2020 (n = 7)	Case series	AR	Customized AR training with virtual limb visualization matched to individual phantom perception, controlled via myoelectric signals; 3 tasks (pick-and-place, imitation, sorting), functional magnetic resonance imaging before and after intervention	45 minutes/session, over 2 weeks	8	SF-MPQ, NRS	NRS: Mean 2.26 (for responding patients)	SF-MPQ: Mean change = -1.884, NRS: 1.31 (mean change = -0.93)	52% reduction in SF-MPQ; 41% reduction in NRS; cortical reorganization correlated with pain relief
Tong et al[25], 2020 (n = 5)	Case series	VR	Immersive VR where intact limb movements control a virtual avatar, providing mirrored visual feedback	4–6 weeks	3–10	VAS, SF-MPQ	VAS: Mean 7.6, SF-MPQ: Mean 16.4	VAS: Mean 6.15, SF-MPQ: Mean 7.06	19.04% reduction in VAS; 56.96% reduction in SF-MPQ; all participants showed pain reduction; improvements in anxiety and depression
Ambron et al[16], 2021 (n = 7)	Clinical trial	VR	Custom VR games controlling avatar legs via motion-tracking sensors on intact/residual limbs	55 minutes/session	5–7 distractor sessions + 10–12 targeted sessions	VAS	VAS: 6.1 ± 2.1	VAS: 3.1 ± 2.1	28% reduction after distractor sessions; 39.6% reduction after targeted sessions
Annaswamy et al[27], 2022 (n = 4)	Pilot study	MR	Home-based use of Mr. MAPP system (mixed reality MT with exergames: Bubble Burst, Pedal, Piano games)	1 month	Daily sessions	NRS, SF-MPQ, Patient-Specific Functional Scale	No clear baseline pain intensity reported	No clear trends in pain scores	Not statistically significant due to small sample size; 1/4 participants reported functional improvement
Lendaro et al[26], 2024 (n = 81)	RCT	XR (VR/AR)	Phantom motor execution using myoelectric pattern recognition to control XR environment vs PMI with guided mental rehearsal	Variable (28–40 weeks total)	15	PRI from SF-MPQ, NRS	Phantom motor execution: NRS: 4.48 ± 2.77, PRI: 14.5 ± 8.78, PMI: NRS: 4.04 ± 2.87, PRI: 14.71 ± 7.28	Phantom motor execution: NRS change = 1.97 ± 0.11, PRI change = 9.35 ± 0.22 PMI: NRS change = 1.25 ± 0.18, PRI change = 10.03 ± 0.45	64.5% (phantom motor execution) and 68.2% (PMI) reduction in PRI; 71% (phantom motor execution) and 68% (PMI) experienced ≥ 50% pain reduction

AR: Augmented reality; MR: Mixed reality; MT: Mirror therapy; NRS: Numerical Rating Scale; PLP: Phantom limb pain; PMI: Phantom motor imagery; PRI: Pain Rating Index; RCT: Randomized controlled trial; SF-MPQ: Short-Form McGill Pain Questionnaire; VAS: Visual Analog Scale; VR: Virtual reality; XR: Extended reality.